NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/comp/unix/question/14898

Text File | 1992-12-22 | 2.0 KB | 41 lines

Newsgroups: comp.unix.questions
Path: sparky!uunet!spool.mu.edu!agate!boulder!ucsu!spot.Colorado.EDU!ushomirs
From: [e-mail] (USHOMIRSKIY GRIGORIY)
Subject: Comparing tapes using cmp
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Organization: University of Colorado, Boulder
Date: Tue, 22 Dec 1992 21:20:42 GMT
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I need to compare a bunch of tapes to see if the files stored on tapes are
identical.  The tapes consist of 6 - 12 files stored in simple blocked format
(i.e. created using dd if=file.on.disk of=tape-device).  I am trying to use
cmp to accomplish this but it is acting quite flakey.  When the block size on
both tapes being compared is the same cmp works perfectly.  But if the block
sizes differ cmp freaks out sometimes.  If I try cmp /dev/tape1 /dev/tape2
then I get an "Invalid argument" error (which I guess means that cmp tried
to read a tape with wrong block size).  If I try being more sly and do
dd if=/dev/tape1 ibs=tape-1-block-size obs=tape-2-block-size | cmp - /dev/tape2
it works most of the time, but sometimes it gives me an error "EOF on /dev/tape2" even if I know that the files are exactly the same.

Does anyone have any idea how to compare tapes of different block size
*reliably*?  All I need to know for comparing purposes is whether the files
are identical or not, I do *not* need to know what lines are different, etc
(the files are binary, so it wouldn't do any good anyway).

I am using a SPARCstation 2 with SunOS 4.1.3.  Tapes I'm trying to compare are
an Exabyte 8mm tape and a 6250 (9-track tape).  Copying tapes to disk and
comparing disk files would not work for me (files are too big and there are too
many of them to bother).

I have tried both the cmp that came with SunOS and GNU's cmp (version 2.0).
Both fail with the same error.

Thanks for any replies.  Please e-mail to [e-mail] if
possible.

Greg